CHEYENNE - The Senate Revenue Committee endorsed a bill Thursday that would tax helium production in Wyoming.

Helium is currently the only mineral commodity in Wyoming not taxed.

If the bill passes, the state will collect a 6 percent severance tax on helium extracted from the ground.

Ed Schmidt, director of the Wyoming Department of Revenue, said helium taxation could mean more than $2 million of additional tax revenue every year.

"(Helium) should be taxed the same way as everything else," Schmidt said.

ExxonMobil, one of the largest global oil and gas producers, questioned whether helium was taxable last year in a lawsuit it won against the state.

In the lawsuit, the Wyoming Supreme Court ruled ExxonMobil shouldn't have to pay taxes because Wyoming didn't own the helium. ExxonMobil leases the right to develop the gas from the federal government.

Patrick Day, an attorney representing ExxonMobil, said the bill would be "unconstitutional" since it would only apply taxes to helium extracted by ExxonMobil.

ExxonMobil is the only company extracting helium in the state. The company pumps helium from natural gas wells in Sublette County.

Matheson Tri-Gas Inc. and Air Products announced plans this month to build and operate a liquid helium plant near Big Piney in 2009.

Day said other companies' plans to extract helium in Wyoming are not enough to show that ExxonMobil wouldn't be unconstitutionally picked out to pay taxes.

"It may go forward, it may happen," Day said. "All those mays don't amount to a real thing."

ExxonMobil pumps 25 percent of the world's annual helium supply from Wyoming.

The bill, House Bill 133, goes to the full Senate for consideration next.